Functions

import java.util.Scanner;

public class Functions {
    // ------------------ EX1 -----------------------------
    /*
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        // declare values
        int number, digit, len;
        int[] nArr;
        // Part 1 of ex1
        System.out.println("Please enter a large number and a digit: ");
        number = sc.nextInt();
        digit = sc.nextInt();
        System.out.printf("The digit %d appears %d times in the number %d\n", digit, checkNum(number, digit), number);
        System.out.println("\n---------------------------------------");
        // Part 2 of ex1 - value from array
        System.out.println("Please enter the size of the numbers array and a digit: ");
        len = sc.nextInt();
        digit = sc.nextInt();
        nArr = new int[len];
        initArray(nArr);

        System.out.printf("The digit %d appears %d times in the given number array", digit, checkNumInArr(nArr, digit));
    }

    public static void initArray(int[] arr) {
        System.out.printf("Please enter %d integers: ", arr.length);
        Scanner s = new Scanner(System.in);
        for(int i = 0; i < arr.length; i++) {
            arr[i] = s.nextInt();
        }
    }

    public static int checkNum(int num, int d) {
        int n = 0;
        do {
            if(num % 10 == d) {
                n += 1;
            }
            num /= 10;
        } while(num != 0);
        return n;
    }

    public static int checkNumInArr(int[] numArr, int d) {
        int sum = 0;
        for(int i = 0; i < numArr.length; i += 1) {
            sum += checkNum(numArr[i], d);
        }
        return sum;
    }
    */

    // ---------------------- EX2 ------------------------
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        //Initializing arrays
        int[] arr1 = {87, 13, 12, 56, 32}, arr2 = {19, 87, 13, 21, 56, 32}, res, util;
        int resLen = arr1.length <= arr2.length ? arr1.length : arr2.length;
        util = new int[resLen];
        // Since the length is unknown the 'checkDuplicates' function
        // copies the duplicate values to the util array and return
        // the number of duplicate numbers in the given arrays
        int len = checkDuplicates(arr1, arr2, util);
        // The res array is initialized with the correct length
        res = new int[len];
        // copyToResultArray function copies the duplicate values to the result array
        copyToResultArray(util, res);
        // printResult displays the duplicate values to the screen
        printResult(res);
    }

    /**
     * The checkDuplicates function gets 3 arrays as an input. The function checks for duplicate numbers
     * in the first two arrays and copies them to the third array (The third array's is initialized
     * in accordance with the shortest array.
     * The function returns the number of duplicates found between the first two arrays
     */
    public static int checkDuplicates(int[] a1, int[] a2, int[] r) {
        int l = 0, index = 0;
        for(int i = 0; i < a1.length; i += 1) {
            for(int j = 0; j < a2.length; j += 1) {
                if(a1[i] == a2[j]) {
                    r[index++] = a1[i];
                    l += 1;
                }
            }
        }
        return l;
    }

    /**
     * A function for copying the values from the first array to the second given array with the right length
     */
    public static void copyToResultArray(int[] u, int[] r) {
        for(int i = 0; i < r.length; i++) {
            r[i] = u[i];
        }
    }

    /**
     * A utility function for printing the values from the result array to the terminal / command line
     */
    public static void printResult(int[] resArr) {
        System.out.print("[");
        for(int n = 0; n < resArr.length - 1; n += 1) {
            System.out.print(resArr[n] + ", ");
        }
        System.out.printf("%d]", resArr[resArr.length - 1]);
    }
}